Prehnite-forming reactions in scapolite-bearing calc-silicate granulites from Rundvågshetta, Lützow-Holm Complex, East Antarctica

We report prehnite-forming reactions in scapolite-bearing calc-silicate granulites from the highgrade metamorphic terrane of Ltzow-Holm Complex, East Antarctica.Based on textural observations, three possible reactions were identified: 1) Prehnite forming from andraditegrossular garnet, 2) Prehnite formation from anorthite, quartz, and calcite, and 3) Prehnite replacing from meionite, quartz, and calcite.Phase equilibrium modeling indicates that prehnite formed under H2O-rich conditions at T = 320-390 C and XCO2 < 0.004.The occurrence of Ferich prehnite reflects Al-Fe 3+ partitioning that occurred during low-grade metamorphism and may serve as an indicator of oxygen fugacity conditions.The prehnite formation reactions exemplify the role of aqueous fluid infiltration during retrograde metamorphism and provide important constraints on changes in fluid conditions from fluid-absent to H2O-rich.